壁に耳あり障子に目あり (かべにみみありしょうじにめあり): walls have ears; walls have ears, sliding doors have eyes

walls have ears; walls have ears, sliding doors have eyes

Walls have ears and paper doors have eyes. A warning to lower your voice, and a reminder that a Japanese room was never built to hold a secret.

The same saying in Chinese: 隔墙有耳

A Japanese proverb (ことわざ)